The present invention relates to an object detection method using an image-pickup device and an object detection apparatus using the method and more particularly, to object detection method and apparatus which, when automatically detecting from a video signal inputted to the image-pickup device objects, such as an object intruding into the range of image-pickup view field, can easily set a masking for a region that differs from a background image within the image-pickup view field range but is not to be detected as an intruding object.
An image monitoring (surveillance) unit using an image-pickup device such as television camera (hereinafter termed as a TV camera) has hitherto been used widely. A monitoring system using such an image monitoring unit as above has however been required to be such a system that an intruding object such as person or automobile being intruding into the monitoring view field of the image-pickup device is not detected manually by an operator who watches an image displayed on a monitor but is automatically detected from an image inputted to an image input means such as a camera.
In order to realize the system as above, a difference between a reference image, such as a reference background image, a previous input image picked up a predetermined earlier or the like and an input image is first detected through, for example, a well-known subtraction method to detect an intruding object in the view field. The subtraction method is a method in which an input image obtained from a TV camera is compared with a reference background image prepared in advance, that is, an image lacking any pictures of an object to be detected so as to obtain a difference or subtracted value in brightness value between the two images for each pixel and a region in which the difference values or the subtracted values are large is detected as the object. Processing of the subtraction method is described in JP-A-7-79429, for instance.